A wireless communication network typically includes multiple cells having corresponding base stations for exchanging communications with mobile devices operating within the cell. The base stations are connected to a centralized system, such as a mobile location center (MLC), for coordinating the communications and interfacing with other networks, such as the public switched telephone network (PSTN) and/or a packet switching network, such as the Internet.
A variety of modern wireless communication services include the feature of determining a geographic location of a mobile device. For example, an emergency service responsive to “911” being initiated at the mobile device includes estimating latitude and longitude of the mobile device in order to locate the device, which is particularly important when a distressed caller is otherwise unable to provide their present location. The geographic location of the mobile device may be determined by a server or other node in the wireless communication network, such as a Mobile Location Center (MLC). The MLC may determine the geographic location of a mobile device operating within the wireless communication network using positioning measurements from a global navigation satellite system (GNSS) or measurements from a terrestrial positioning system.
Location determinations based on GNSS measurements are generally more accurate than terrestrial measurements, although there are exceptions. For example, GNSS positioning may not be effective in urban environments or indoors, where structures obscure access to multiple satellites, or otherwise weaken signal strengths, or introduce multi-path components to the signals. Therefore, conventional systems for determining geographic locations of mobile devices typically rely on GNSS measurements, and resort to terrestrial measurements only when GNSS measurements are not available or fail to provide reliable results. Conventional systems may also combine GNSS and terrestrial measurements by requesting and using them in a linear fashion. This approach is time-consuming, and does not necessarily result in the most accurate geographic location determination.
In a representative embodiment, a method is provided for an MLC to determine a location of a mobile device in a wireless communication network. The method includes receiving a request initiated by the mobile device to determine the location of the mobile device; concurrently requesting global navigation satellite system (GNSS) measurements from the mobile device and terrestrial measurements from transceivers in the wireless communication network, and receiving the GNSS measurements and at least one of the terrestrial measurements. A GNSS location of the mobile device is calculated as a function of the received GNSS measurements, and the calculated GNSS location is determined to be the location of the mobile device when the calculated GNSS location meets a predetermined accuracy threshold. A terrestrial location of the mobile device is calculated as a function of the received terrestrial measurements, and the calculated terrestrial location is determined to be the location of the mobile device when the calculated terrestrial location meets the predetermined accuracy threshold. A hybrid location of the mobile device is calculated as a function of the received GNSS measurements and the received terrestrial measurements when neither the calculated GNSS location nor the calculated terrestrial location meets the predetermined accuracy threshold. The calculated hybrid location is determined to be the location of the mobile device when the calculated hybrid location meets the predetermined accuracy threshold.
In another representative embodiment, a system is provided for determining a location of a mobile device in a wireless communication network. The system includes an MLC configured to determine a first location of the mobile device and a corresponding first accuracy as a function of first measurements, to determine a second location of the mobile device and a corresponding second accuracy as a function of second measurements, and to identify one of the first location and the second location as the geographic location of the mobile device when any one of the first or second accuracies exceeds a predetermined threshold.
In another representative embodiment, a method is provided for an MLC to determine a geographic location of a mobile device in a wireless communication network. The method includes concurrently requesting global navigation system (GNSS) measurements from the mobile device and terrestrial measurements from nodes in the wireless communication network. A first location of the mobile device is calculated as a function of the GNSS measurements, a second location is calculated as a function of the terrestrial measurements, and a third location is calculated as a function of both the GNSS measurements and the terrestrial measurements. One of the first, second or third locations having a highest accuracy is selected as the geographic location of the mobile device.